1. Field of the Invention
The present invention relates to a relay driving apparatus, and is suitably applied to a relay driving circuit in a television set.
2. Description of the Related Art
There has been hitherto known a relay driving circuit for opening/closing a main power source switch in a television set or the like on the basis of an operating signal supplied from a remote controller or the like.
The relay driving circuit is equipped with a main power source switch, a relay coil and a variable iron piece therein, and when the variable iron piece is attached (attract) to the iron core inside the relay coil by the relay coil, the main power source switch is turned on interlockingly with the adsorption operation.
In the case where the main power source switch is made to operate under on-state, when a user carries out a predetermined input operation to turn on the main power source switch in the television set through input means such as a remote controller or the like, the relay driving circuit receives an operating signal supplied from the remote controller or the like, and in response to the operating signal the relay driving circuit supplies a rated voltage to the relay coil.
The rated voltage can make the relay coil generate enough magnetic force to move the movable iron piece and attach it to the iron core. Therefore, under application of the rated voltage, the movable iron piece disposed away from the iron core inside the relay coil is moved and attached to the iron core by the relay coil, thereby turning on the main power source switch which operates interlockingly with the attachment operation.
Under the state that the main power source switch is set to an on-operation state (that is, the movable iron piece is attached to the iron core of the relay coil), the relay driving circuit supplies a holding voltage in place of the rated voltage which has been supplied until now.
With the holding voltage, the relay coil which makes the movable iron piece be attached to the iron core can generate enough magnetic force to keep the attachment state, whereby the relay coil keeps the movable iron piece to be attached to the iron core. Accordingly, the on-state of the main power source switch is kept, and the main power is supplied to each circuit portion in the television set.
In the relay driving circuit thus constructed, the voltage for keeping the attachment of the movable iron piece (holding voltage V2) is set to about the half of the rated voltage V1. The power consumption in this case is equal to about a quarter of the power consumption when the on-state of the main power source switch is kept with the rated voltage of V1 at all times.
However, when the movable iron piece is detached from the iron core due to reduction of AC (Alternating current) voltage, an external impact or the like under the state that the main power source switch is kept under the on-state, it has been hitherto difficult for the relay driving circuit to attach the movable iron piece to the iron core again and restore the main power source switch to the on-state.
The present invention has been implemented in view of the foregoing description, and has an object to provide a relay driving apparatus which can enhance the operation reliability with promoting energy saving.
In order to attain the above object, a relay driving apparatus for temporarily subjecting a relay to a rated-driving operation to shift the relay to a driving state by supplying a predetermined rated voltage to the relay, and then reducing the voltage to keep the driving state of the relay, is characterized in that the driving state of the relay is monitored, and on the basis of the monitoring result, the relay is subjected to the rated driving operation or the rated voltage is periodically supplied to the relay kept under the driving state, thereby enhancing the operation reliability with promoting energy saving.